This invention relates to polyester resins containing an effective amount of C.sub.10 hydrocarbon concentrate i.e. dicyclopentadiene, or other C.sub.5 codimers. The polyester resins are prepared by the hydrolysis of unsaturated dicarboxylic acid anhydrides and the in situ generation of Diels-Alder products such as carbic anhydride.
More specifically, the invention relates to polyester resins produced by reacting a polyol, an olefinically unsaturated dicarboxylic anhydride, water, and an effective amount of C.sub.10 hydrocarbon concentrate wherein the anhydride and water are first reacted, the C.sub.10 concentrate is reacted, carbic anhydride is formed by heating and the polyol is finally reacted into the mixture.
It is well known from the report by P. L. Smith, et al. "The Use of Dicyclopentadiene in Polyesters", Proceedings of the 22nd Annual Technical Conference S.P.I., Reinforced Plastics Division, Washington, D.C. (1967) and the article by R. Zimmerman, et al. "Modification of Unsaturated Polyesters with Dicyclopentadiene", Fette-Seifen-Anstrichmittel 66, #9, 670-678 (1976), and U.S. Pat. No. 3,347,806 that polyesters can be modified with a concentrated dicyclopentadiene extract.
It is also known from U.S. Pat. No. 4,148,765 dated Apr. 10, 1979, that polyester resins containing dicyclopentadiene can be improved by hydrolysis of the unsaturated dicarboxylic anhydrides used therein prior to the reaction of the dicyclopentadiene.
Low profile polyester resins are known from U.S. Pat. No. 3,883,612 dated May 13, 1975, and U.S. Pat. No. 3,986,992 dated Oct. 19, 1976. However, these polyesters depend upon polymer additives to give the low profile or low shrink properties.